1. Field of the Invention
The present invention relates to image process apparatus and method for adding predetermined additional information to an input image, and a storage medium for storing the image process method.
2. Related Background Art
In recent years, since performance of an image process apparatus such as a color printer, a color copy machine or the like has been improved, the image process apparatus has become possible to form a high-quality image. In such condition, since there is some fear that a negotiable paper such as a bank note or the like is forged, various forgery prevention techniques have been developed.
As one of these techniques, there is such an addition system (or add-on system) as a dot pattern representing additional information such as a machine number of the image process apparatus or the like is printed in addition to a color image.
Since this dot pattern is periodically printed on an entire image plane, the additional information is added to only an yellow printing plane.
Further, in recent years, to save a data amount handled in a host computer or a printer or to cause the printer to print a high-quality halftone image, various kinds of conversion methods (i.e., halftone process methods) such as a dither method, an error diffusion method and the like have been selectively executed.
In such condition, since each image process apparatus has only one of the above various add-on systems, the image process apparatus always adds on the additional information by using one system.
Therefore, for example, there is a case where the predetermined add-on system is not suitable for a certain conversion method (i.e., halftone process method) such as a dither process or the like in the plural conversion methods. In this case, there is a problem that it is difficult to read the add-on image and thus analyze the contents of the additional information. This is because, even if the dot pattern is buried in the image after performing the conversion process such as the dither process or the like, a position at which the dot pattern was buried can not be judged or found from the after-processed image.
Further, in a case where affinity between the conversion method and the add-on system is wrong, the dot pattern is remarkable on the image which was printed by using such the conversion method (i.e., halftone process method). Therefore, there is also a problem that image quality of such the image is substantially deteriorated.
The present invention was made in consideration of the above-described related background art, and a main object thereof is to enable, in a case where an input image is image-processed selectively by using plural conversion methods (i.e., halftone process methods), a user to use the processed image as an original image by burying additional information in the input image without deteriorating image quality thereof as much as possible, and to enable the user to certainly decrypt or decode the additional information added to the input image.
Concretely, the object of the present invention is to add the appropriate additional information to the input image even if the plural conversion methods are switched and used.
In order to attain the above object, according to one preferred embodiment of the present invention, there is provided an image process apparatus comprising:
a generation means for generating an image signal;
an image conversion means for performing image conversion on the image signal by selectively using one of the plural image conversion methods;
a generation means for generating the predetermined additional information;
a selection means for selecting an additional method to add the predetermined additional information to the image signal, according to the image conversion method used when the image conversion means performs the image conversion on the image signal; and
an additional means for adding, in the addition method selected by the selection means, the predetermined additional information to the image signal in a state that the added information is difficult to be perceived by human eyes.
An another object of the present invention is to add, even if the plural conversion methods are switched and used, the appropriate additional information to the input image according to a position or a period at which each conversion process is performed.
In order to attain the above object, according to one preferred embodiment of the present invention, there is provided an image process apparatus comprising:
a halftone process means for generating an image signal, and performing a halftone process on the image signal by selectively using one of plural halftone process methods;
a generation means for generating the predetermined additional information; and
an addition means for adding the predetermined additional information to the image signal in the state that the added information is difficult to be perceived by the human eyes, according to a spatial frequency of a halftone cell corresponding to the halftone process method selected by the halftone process means and a writing start position of the image signal.
A still another object of the present invention is to add, even if the plural conversion methods are switched and used, the additional information to the input image suitable for all the conversion methods.
In order to attain the above object, according to one preferred embodiment of the present invention, there is provided an image process apparatus comprising:
an input means for inputting an image signal; and
an addition means for adding a pattern which is obtained by combining plural dots each composed of first and second areas of which longitudinal directions are different from each other such that the pattern represents the additional information, to the image signal inputted by the input means, in the state that the added pattern is difficult to be perceived by the human eyes.